China is investing in poor nations all over the world. These investments seem altruistic, but somehow they never turn out that way. Its Belt and Road Initiative, by which it funds infrastructure projects in poorer nations the world over, puts those nations in China’s debt.
Those who are worried about this debt essentially see China doing something similar to the scam that the robber barons of the gilded age carried out: The companies would have stores that would give employees credit. However, the company would never pay the employees a sufficient salary to enable them to get out of debt. That debt meant the employees were trapped working for the company forever, at starvation wages, with terrible working conditions.
Belt and Road Initiative is basically meant to help move millions of Chinese out of China and expand into other countries. The rest is just window dressing.